A three-dimensional collagen lattice activates NF-kappaB in human fibroblasts: role in integrin alpha2 gene expression and tissue remodeling.
Normal adult human dermal fibroblasts grown in a three-dimensional collagen lattice increase mRNA level of collagen receptor integrin subunit alpha2 (Xu, J., and R.A.F. Clark. 1996. J. Cell Biol. 132:239- 249.) and DNA binding activity of a nuclear transcription factor, NF-kappaB (Xu, J., and R.A.F. Clark. 1997. J. Cell Biol. 136:473-483.). Here we present evidence that the collagen lattice induced the nuclear translocation of p50, one member of NF-kappaB family, and the degradation of an NF-kappaB inhibitor protein, IkappaB-alpha. The inhibition of NF-kappaB activity by SN50, a peptide inhibitor targeted at nuclear translocation of NF-kappaB, significantly reduced the induction of integrin alpha2 mRNA and protein by the collagen lattice. A region located between -549 and -351 bp in the promoter of integrin alpha2 gene conferred the inducibility by three-dimensional collagen lattice. The presence of either SN50 or IkappaB-alpha32, 36, a stable mutant of IkappaB-alpha, abrogated this inducibility, indicating that the activation of integrin alpha2 gene expression was possibly mediated by NF-kappaB through this region. Although there were three DNA-protein binding complexes forming in this region that are sensitive to the inhibition of NF-kappaB nuclear translocation, NF-kappaB was not directly present in the binding complexes. Therefore, an indirect regulatory mechanism by NF-kappaB in integrin alpha2 gene expression induced by three-dimensional collagen lattice is suggested. The involvement of NF-kappaB in reorganization and contraction of three-dimensional collagen lattice, a process that requires the presence of abundant integrin alpha2beta1, was also examined. The inhibition of NF-kappaB activity by SN50 greatly blocked the contraction, suggesting its critical role in not only the induction of integrin alpha2 gene expression by three-dimensional collagen lattice, but also alpha2beta1-mediated tissue-remodeling process.
Xu
J
J
Department of Dermatology, School of Medicine, State University of New York, Stony Brook, New York 11794-8165, USA. JXu@epo.som.sunysb.edu
Zutter
M M
MM
Santoro
S A
SA
Clark
R A
RA
D000328:Adult; D015703:Antigens, CD / Q000235:genetics*; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D003094:Collagen / Q000737:chemistry* / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000378:metabolism; D005347:Fibroblasts; D005782:Gels; D005786:Gene Expression Regulation; D006801:Humans; D020672:I-kappa B Proteins; D039421:Integrin alpha2; D016023:Integrins / Q000235:genetics*; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism / Q000502:physiology*; D052002:NF-kappa B p50 Subunit; D010455:Peptides / Q000378:metabolism; D011401:Promoter Regions, Genetic
D015703:Antigens, CD; D004268:DNA-Binding Proteins; D005782:Gels; D020672:I-kappa B Proteins; D039421:Integrin alpha2; D016023:Integrins; D016328:NF-kappa B; D052002:NF-kappa B p50 Subunit; C000606204:NFKBIA protein, human; D010455:Peptides; C118258:SN50 peptide; D000072000:NF-KappaB Inhibitor alpha; D003094:Collagen